Something in my post count (can't quite put my finger on exactly WHAT it is...

) should tell you that I have not been too afraid to comment on photos in the past (and my post count does not derive from active participation in topics in the Off Topics from times back when they still counted), and I still like to pass comments to people's submissions here. When time allows for it, I look at many photos and like to comment on quite a few.
There are images that don't activate any desire inside me to comment. Some are simply too snapshotty and too boring to really inspire me to anything. And if to speak the much dreaded word "snapshot", explaining then WHY this particular photo seems to be no more than that, would do said photo too much honour already, I much rather don't say anything at all. Some photos that get 50 replies and no comments should tell the poster something for THAT fact alone...
Sometimes the subject matter doesn't speak to me. Same as flowers don't speak to Schumionbike, cars don't speak to me ever. Nor do photos of guns or other weapons.
One kind of photography that I know NOTHING about and therefore can NOT comment on, other than expressing personal feelings, are studio photos. I know next to nothing about proper lighting nor studio set-ups or posing people. That is when I feel I best not say anything.
Sometimes, however (time permitting), I go on 0-reply sprees. I go to the forums, and back to the latest page still showing, scan it for all 0-reply pics, and try to think of something to say. Often I wrap my comments/critiquing into questions to the OP about the why they did it in the way they did. I find asking questions is a lot more communicative and a lot less hurting - even those who are very delicately "skinned" should come out of being asked a question unhurt.
There have been photos that even passed my 0-reply sprees uncommented. They were then those that I described earlier.
Other than that: photos that already have 17 replies no longer need my saying "I think the same!", or my adding another "Wow, marvellous!", though such positive remarks usually feel good, of course. The more, the better? Oh well...